Electronic musical apparatus



y 20, 1969 J. MARKOWITZ ET AL 3,445,579

ELECTRONI (I MUS I CAL APPARATUS Filed Feb. 8, 1965 Sheet INVENTO/PS.JEROME MARKOW/TZ ERHOLD ER/POL ROBERT GRIFFITH JAMES R/CHARD WETH 19V 70PREAMI? ATTORNEYS.

J. 'MARKOWITZ ET AL 3,445,579

ELECTRONIC MUS I CAL APPARATUS Sheet. & of 3 May 20, 1969 Filed Feb. 8,1965 INVENTO/PS. JEROME MAR/(OM07? [IV/POL R08E/P7' GRIFFITH JAMESRICHARD WETHERHOLD ATWRNEKS'.

20, 1969 J. MARKOWITZ ET AL 3, 5,579

ELECTRONIC MUSICAL APPARATUS Sheet Filed Feb. 8, 1965 w o w WW 6/ T If ma mu: 51m!- RR A A H Mum m mm: RRM ERA JEJ B 2 H ED 0 m ATTORNEYS.

United States Patent 3,445,579 ELECTRONIC MUSICAL APPARATUS JeromeMarkowitz, Allentown, Errol Robert Grilfith,

Topton, and James Richard Wetherhold, East Texas, Pa. (all Allen OrganCompany, Macungie, Pa. 18062) Continuation-impart of application Ser.No. 275,380,

Apr. 24, 1963. This application Feb. 8, 1965, Ser.

Int. Cl. Gh 1/02, 3/00; G10c 3/06 US. Cl. 84--1.24 13 Claims ABSTRACT OFTHE DISCLOSURE An electronic musical instrument having a keyboard andpiano action transduces the action movement into a musical tone,preferably having the tonal qualities of a piano. Electronic andacoustical components are used to produce musical tones without the aidof strings or a conventional sounding boar-d. A knock sound generatingdevice is included to duplicate the knock sound typical of conventionalpianos.

In general, this invention relates to a new and improved electronicmusical apparatus utilizing electronic and acoustical techniques forproducing the sound of aconventional piano and/or organ. Moreparticularly, it is directed to an electronic piano which may beutilized with any of the known piano actions with the same degree ofcontrol as presently possible with conventional pianos.

This application is a continuation-in-part of application Ser. No.275,380 for Electronic Musical Apparatus, filed Apr. 24, 1963 now UnitedStates Patent 3,248,470.

The conventional piano produces its characteristic tone by an actionconsisting primarily of mechanical levers by means of which a felthammer can be caused to strike one or more taut steel strings with awide range of velocity and force causing the strings to vibrate. Thesevibrations are transmitted to a sounding board for amplification. Anextremely high order of control can be exerted on the amplitude andother tonal characteristics of the sound by a skilled performer. Thewide range of amplitude results mainly from the construction of themechanical linkage between the key which is struck by the performer andfelt hammer.

In the past, electrification of pianos has fallen along certainconventional lines. That is, developments in the past have been directedto the electrical amplification of the sound produced by a piano. Thesetechniques included utilizing the strings to excite electromagnetic orelectrostatic pick-ups, or by having the hammer strike vibrating reedswhich produced output signals in accordance with the mode of theirvibration. However, these techniques produced pale imitations of thesound produced by a conventional piano and were therefore not acceptableexcept as novelty items.

In accordance with the teachings of the present invention, an electronicpiano is disclosed which utilizes a conventional piano action, pluselectronic means for producing an electrical signal which when amplifiedand transduced by a suitable speaker will produce a piano-type tone. Apiano constructed with the electronic means of the present inventionresembles a conventional piano in respect to the keyboard and keyaction, but the strings and conventional sounding board are replaced byelectronic and acoustical components.

In accordance with the present invention, the electronic means isoperative from the felt hammer of the piano action to produce a signalin acordance with the velocity of the hammer. This is similar to theoperation of the strings 3,445,579 Patented May 20, 1969 of aconventional piano. Each note on the piano scale is producedelectronically with its amplitude dependent upon the force and velocityof the hammer.

It has been recognized that the tonal characteristics of a piano are acombination of many factors including the vibration of the string. Amongthese factors that make up the basic tonal characteristics of a piano isthe knock which occurs the beginning of every note'when a piano strings.However, in an electronic piano of the type disby the impact sound ofthe hammer against the strings which is transmitted and in effectamplified by the sounding board. It is one of the objects of the presentinvention to provide an electronic piano which acoustically reproducesthe knock effect.

One step in adjusting the action of a conventional piano involves therealignment of the shank and hammer with the strings. This is normallyacomplished by simple observation of the hammer through the spacingbetween strings. However, in an electronic piano of the type disclosedherein such observation is not readily made. Accordingly, it is anobject of the present invention to provide a means whereby the magneticcore mounted on the action hammer may be properly aligned with thetransducer coil.

In the construction of an electronic piano, it has been found that thecoils used for transducing the piano action into an electronic signalhave a transformer action caused by their close juxtaposition. Thistransformer action may result in the production of unwanted notes. Ittherefore is an object of the present invention to provide a novel meansfor isolating the coils to avoid the foregoing described problem.

Electronic pianos constructed in accordance with the present inventionuse magnets mounted upon the action hammers. As in conventional pianos,these hammers are mounted in close side-by-side relationship. Themagnets are in such close proximity that movement of the magnet when theaction key is struck causes adjacent magnets and hammers to moveslightly. This movement may result in the production of unwanted noiseand a lowering of the efiiciency of the action. Accordingly, it isanother object of the present invention to provide a magnetic barrierfor isolating the magnets from one another to avoid movement of adjacentaction hammers.

It has been determined that the construction of an electronic piano musttake into account factors other than the production of the musical note.For example, it is also necessary to take into consideration the effectof the instrument upon the player. This may be referred to as apsycho-acoustic effect. In a conventional piano the psychoacousticeffect manifests itself in the transference of vibrations from thesounding board back into the piano keys. The player feels thesevibrations in his fingers and it could affect his playing when it is notpresent. It therefore is still another object of the present inventionto provide a means whereby the vibration caused by the generation ofsound is transferred back into the piano keys where it may be felt bythe player.

Therefore, it is a general object of this invention to avoidtheforegoing and other difficulties of the prior art and to achieve theresults discussed above by a provision of a new and improved pianoutilizing electronic tone generating techniques.

A further object of this invention is the provision of a new andimproved electronic piano capable of producing musical tones directlyfrom the piano action by electronic components substituted for thestandard strings and sounding board.

A still further object of this invention is the provision of a new andbetter electronic piano which utilizes a velocity sensitive transduceroperative from the felt hammer of a piano action to produce a piano-typetone normally associated with the particular key being struck.

Another object of this invention is to produce a new, better and lighterweight piano which incorporates all of the features of tone variationpossible in conventional pianos.

Still another object of the present is the provision of a new and betterpiano which requires tuning only at infrequent intervals by utilizationof electronic sound producing components.

Yet another object of this invention is to provide an electronic tonegenerator capable of producing a pianotype tone in response to avelocity sensitive key action and/or to produce an organ-like sound ofsustained amplitude when operated from an organ-type key contactarrangement.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there are shown in thedrawings forms which are presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIGURE 1 is a perspective view of an electronic piano with a portionthereof cut away to show the knock producing apparatus.

FIGURE 2 is a bottom plan view of the piano shown in FIGURE 1.

FIGURE 3 is a side view of a piano action incorporated in the instrumentshown in FIGURE 1.

FIGURE 4 is a top plan view of the transducing coils for the musicalinstrument taken along the line 4--4 of FIGURE 3.

FIGURE 5 is a partial top plan view of the piano action shown in FIGURE3 taken along the line 55.

FIGURE 6 is a sectional view of a transducer coil taken along the line6-6 in FIGURE 3.

FIGURE 7 is a schematic showing the electronic means for producing thepiano tone associated with the action of FIGURE 3.

FIGURE 8 is an alternate embodiment showing the electronic means forproducing the piano tone associated with the action of FIGURE 3 and anelectronic knock producing circuit.

Referring now to the drawings in detail, wherein like numerals indicatelike elements, there is shown in FIG- URE 1 a perspective view of theelectronic piano and/ or organ of the present invention designatedgenerally as 10. The electronic piano is shown mounted in the case of aconventional grand piano.

As shown, the piano 10 includes a keyboard 12, and pedals 14. Thekeyboard 12 consists of a plurality of keys 16 mounted in conventionalside-by-side relation.

One of such keys 16 and its action 18 is shown in FIG- URE 3. The action18 is of the type which may be used in a grand piano.

The action 18 includes a key 16 mounted on a key frame 20 for pivotalmovement about a balance rail 22. The balance rail 22 has an upstandingbalance key pin 24 extending through a hole provided in the key 16. Thekey frame 20 has a pair of cushions 26 and 28 associated with each endof the key 16 to insure a smooth limit stop for the movement of the key16. The piano action 18 is intended to transmit pivotal movement of thekey 16 into upward movement of the hammer 30 which is attached to asuitable hammer shank 32. The hammer shank 32 is pivotally secured atthe pivot point 34 to the hammer butt 36. The hammer butt 36 is mountedon the frame 38 by means of a pin 40 which threadedly engages the frame38. The pin 40 may be loosened to adjust the angular position of hammer30.

The hammer shank 32 rests on a hammer rest 41. The hammer shank 32 has ahammer shank roller 42 associated therewith resting on a suitable jackor grand fiy 44.

The key 16 has a capstan screw 46 integral therewith and utilized totransmit rotative movement to a suitable wippen 48 pivoted about theframe 38. The jack 44 is pivoted about the other end of the wippen 48 sothat upward movement of the screw 46 causes the jack 44 to force theroller 42 of the hammer shank 32 upwardly to provide upward movement ofthe hammer 30. The jack 44 is guided in this movement by an escapementlever 50 pivotally mounted about a top flange of the wippen 48. The jack44 is further returned to its initial position by a suitable repetitionspring 52 and the escapement lever 50 is returned to its initialposition by a repetition spring 54 to thus aid in biasing the key 16 toits released position shown in FIGURE 3.

The key 16 has a hammer check 56 mounted at the end thereof to cushionthe return of the hammer 30 after the completion of a stroke.

All the elements discussed above form a portion of the grand pianoaction 18 and are conventional. Any type of piano action, such as anupright action, could be utilized in place of the grand piano action 18.

The hammer 30 has at its striking end a cushion 58 surrounding a magnet60. The magnet 60 is adapted to enter a suitable opening 62 in a coil 64mounted above the hammer 30. The opening 62 is best shown in FIGURES 4and 6. When the key 16 struck by the player, the coil 64 acts as atransducer for the electric piano tone generator 66 associated with theparticular piano action 18 discussed previously. The coil 64 transducesthe movement of the magnet 60 on hammer 30 directly into an electricpulse proportional to the velocity thereof.

As stated earlier, the importance of the piano rests upon its powerfuland finely and graduated tone and its convenience for the production ofconcerted music. Thus, the electronic piano tone generator 66 must becapable of utilization with a piano action of the general type tocontrol one or more electronic oscillators. Further, means must beincluded in the piano generator to control the amplitude, decaycharacteristic, and the pulse length of the oscillator to vary the tonesproduced thereby.

The circuitry forming the piano tone generator 66 may utilize twoseparate generating circuits which are utilized to stimulate the soundgenerating from a two-string tone. In a conventional piano, the stringsare steel wires of graduated thickness and length, the larger being madeheavier by being wound with copper wire. For each of the extreme lowertones, only one wire is provided, but for most others, there are two orthree wires which are tuned in unison and placed so that they will besimultaneously struck by a single hammer. The tone generator 66 isassociated with a key adapted to produce one of the middle notes on thepiano scale utilizing two strings struck in unison.

The components of the circuit 66 will be discussed in an integrateddiscussion of their operation. Certain of the elements drawn in fulldetail in other figures are shown schematically in FIGURE 7. However, tosimplify understanding of the invention they have been assigned likenumerals.

The coil 64- has one terminal connected to a source of supply Eb and itsother terminal to the base terminals 68 and 168 of transistors 70 and 72respectively. The magnet 60 is a permanent magnet attached to the hammer30 which will enter the coil 64 with a velocity that will beproportional to the velocity with which the key 16 is struck. Since theinduced voltage in a coil is determined by the number of flux lines cutper unit time, the voltage developed across the coil 64 will beproportional to the velocity of the struck piano key within limits.

The coil 64 voltage is applied between the base 68 and emitter 74 oftransistor 70 causing it to conduct and resulting in the charging ofcapacitor 76 from the source Eb. The charge on capacitor 76 causes thetransistor 78 to conduct and, in so doing, applies the voltage Eb to aHartley oscillator 80. The oscillator 80 includes a transistor 82 havinga split inductance 84 utilized to tune the collector circuit of thetransistor 82.

The conductivity of transistor 7 8 varies with the charge on capacitor76 or, in other words, with the voltage induced in the coil 64. Theoscillator 80 operates in a manner whereby the output will be a soundwave whose amplitude will be approximately proportional to the inputvoltage. The output of the Hartley oscillator 80 is applied through awave shaping circuit 85 to the audio output and loudspeaker means 86.The wave shaping circuit 85 is a standard means of imparting a stringquality on the amplified and transduced sound.

In a conventional piano, there is normally provided a damper which willdamp the string after the key is returned to its initial position. Thisdamping is achieved in the piano tone generator 66 of the presentinvention by utilizing a switch 88 located below the key 16. Thecontacts 88 are opened when the key is struck and closed when the key isin its normal position. After a key is struck and the capacitor 76 hascharged as discussed previously, it discharges through a high resistanceresistor 90 and transistor 78 so that it has a long time delay as wouldbe normal when striking an undamped key on a piano. However, when thekey is released and returns to its up or closed position, the capacitor76 can discharge through diode 92, low resistance resistor 94, and thenowclosed contacts of switch 88 to ground. The capacitor 76 voltage willthus be quickly reduced to zero voltage and the oscillator 80 will ceaseto oscillate.

A second switch 96 is connected in series with the switch 88 and everyother switch 88 associated with each key of a piano to perform thefunction of the sustaining pedal on the piano. The sustaining pedal on aconventional piano prevents the dampers associated with every key fromdampening the vibration of their associated keys. The sustaining switch96 performs its function by allowing the voltage on capacitor 76 tocontinue to decay through the resistor 90 and transistor 78 by openingthe circuit between resistor 94 and ground. The switch 96 may beoperated by the pedals 14 shown in FIG. 1. The tone produced by strikingthe key 16 will decay for a period of time after the key has beenreleased in the same manner as a conventional piano whose sustainingpedal has been depressed.

The portion 98 of the tone generator 66 has substantially the samecomponents as the portion 61, as it is merely intended to reproduce astring exactly similar to the string reproduced by the portion 61 in thesame manner as a two string tone on a conventional piano. The portion 98will be controlled in the same manner and simultaneously with theportion 61, and will provide the additional amplitude plus any possibleinterference effects which result from slight differences between thetwo identical circuits. The portion 98 has been noted with numeralsexactly one hundred more than its associated components in portion 61.For example, the oscillator 180 is similar to the oscillator 80discussed previously.

In a complete piano built in accordance with the principles of thepresent invention, each key will be associated with a similar set ofcomponents as described heretofore, but tuned to the required frequency.The sustaining contacts of switch 96 would connect to a common bus 200associated with all the contacts similar to the contacts of switch 88.Isolating diodes would be provided between each key to preventinteraction of the oscillators.

As indicated above, the mechanical arrangement may be provided so thatthe contacts of switch 96 would be actuated by the foot pedal 14.Further, the piano could be designed to prevent a separate pedal whichwould sustain only the bass notes rather than all of the notes.Additionally, a sostenuto pedal could insure the sustaining of a toneafter the particular key had been struck. Still further, a soft pedalcould be provided to act as an electronic substitute for theconventional soft pedal by switching out one portion of each tonegenerator having more than one oscillator. This would lessen theamplitude of the output signal of the tone generators in the same manneras is now done on conventional pianos. In the alternative, the

soft pedal could proportionately lessen the amplitude of the outputsignals of the tone generator.

The tone generator 66 can additionally be utilized with a separate setof organ keys for producing an organ-like sound of sustained amplitudeeither separately or in combination With the piano discussed above. Theorgan keyboard has been shown representatively by the organ key 98. Theorgan key 98 rotates about a fulcrum 100 to open and close associatedcontacts 110. They key 98 is spring-loaded to an open position by aconductive spring 112 connected to the source voltage Eb. Upon pressingthe key 98, contacts are closed completing a circuit from the voltagesource Eb through a resistor 114, capacitor 116 and wave shaping circuitthrough the input of transistor 182 in oscillator 180.

In the interest of economy, the organ contacts could be placed below thepiano key 16 and suitable switches arranged in a circuit to cut out thepiano signal transducer as well as connecting the organ contact to theoscillator and vice versa.

As shown in FIGURE 1, the keys 16 are arranged in side-by-side relation.Accordingly, the actions 18 and coils 64, associated with each key arealso arranged in side-by-side relation. This is best illustrated inFIGURES 4 and 5. In FIGURE 4, the coils 64 for the respective hammersare shown. In FIGURE 5, the hammer shanks 32 are shown pivotallyconnected to the adjustable hammer butts 36 on frame 38. As has beenindicated previously, the close juxtaposition of the actions 18 andcoils 64 may create problems of inductive and magnetic coupling.Moreover, the nature of the coil structure and its mount to be describedmake it difficult to adjust the angular position of hammer butts 36 andhammers 30 so that magnets are properly aligned with openings 62. Thenovel solution to these problems will be set forth in the followingdetailed description of coils 64 and their mounts.

The coils 64 are supported above the hammers 30 by means of uprightbrackets 120, one of which is shown in FIGURE 3. The brackets support apair of transverse rails 122 and 124 which extend across the actions 18.Each coil 64 depends from a plate 126 above its associated hammer 30.The coils 64 and plates 126 are positioned on the rails 122 and 124 sothat the magnet 60 will enter opening 62 when key 16 is struck.

Coil 64 is tightly held against plate 126 by means of a pair of threadedfasteners 128 and 130. The fasteners 128 and 130 may be made of anon-magnetic material to avoid interference with the magnetic propertiesof coil 64. The plate 126 is rigidly fastened on rails 122 and 124 bymeans of a pair of threaded fasteners 132 and 134.

As indicated above, a step in adjusting the action of the musicalapparatus 10 is to adjust the alignment between hammer 30 and opening 62in coil 64 by means of pin 40. Since the hammers are below the coils 64which are positioned close together, it is difficult to see the magnets60 to properly align them with openings 62. In order to overcome thisproblem, the plates 126 are made of a transparent plastic material suchas Lucite. By providing this transparent material, it is made possibleto observe the magnets 60 while aligning them with openings 62.

As best shown in FIGURE 4, the coils 64 are closely spaced together. Asa consequence of this close spacing, it has been found that when a pulseis generated in one of the coils 64 it is inductively coupled to anadjacent coil. The inductive coupling may be suflicient to generate avoltage pulse which will initate an unwanted tone. To prevent inductivecoupling of sufficient magnitude to cause generation of unwanted tones,each of the coils 64 is wrapped with an outer layer of a nickel-ironalloy having high permeability, particularly at low flux densities.Nickel-iron alloys having these characteristics are known as permalloy,hipernik, supermalloy, and mu-metal. This has the property of isolatingthe coils 64 so as to prevent inductive coupling.

As is the case with the coils 64, the hammers 30 and their magnets 60are spaced apart by short distances with the result that individualmagnets 60 tend to interact with each other. This interaction manifestsitself in two ways. First, the upward movement of a magnet 60 tends topull adjacent magnets a short distance upwardly. This movement istransferred back into the keys and is apparent on the keyboard. As aconsequence, it may seriously aifect the ability to play successiveadjacent notes. To avoid this problem, a magnetic shield 138 extendsbetween brackets 120 behind the hammers 30. The magnetic shield 138 iscurved so that it may be positioned as close as possible to the magnets60 without interfering with the movement of hammer 30. The magneticshield 138 is made of a magnetic material such as iron or steel. Iteffectively breaks up the magnetic field extending around eachindividual magnet so as to reduce magnetic interaction. Accordingly thestriking of one key 16 and movement of its associated hammer 30 andmagnet 60 has no effect on adjacent keys, hammers and magnets.

As has been indicated previously, it is desirable to pro vide anelectronic piano with the tonal characteristics of a conventional pianoknown as knock. This can be accomplished acoustically in the followingmanner. A sound conducting rod 140 is fixedly mounted to one of therails 122 and 124 that support plates 126 and coils 64. When the key 16is struck, hammer 30 impacts the cushion 58 against coil 64, causing, inaddition to the electronic pulse, a single acoustic pulse of energy.This energy is normally of such a nature that it would hardly be heardexcept that it is transmitted through acoustic conducting rod 140 into asounding board 142 fixedly mounted on top of rod 140. Although thesounding board 142 is shown as a box-like structure having its bottomside open, it may take any one of several configurations. For example,it would be a board or a tuned cavity. The sounding board 142 ispreferably made from long grained wood such as spruce. The soundingboard 142 is constructed in accordance with principles known to thoseskilled in the art.

The sound board couples the acoustic energy pulse to air, which in turnradiates it in the same manner that a normal sounding board of a pianowould radiate such energy. Since this is a pulsing device, striking anygiven key, plurality of keys or sequential series of keys will result ina collective burst of sound substantially the same as that which occursin a piano.

Although it is possible to use a single sounding board 142 coupledthrough the rail 124 and rod 140 to each of the coils 64, it has beenfound that a better result can be achieved by using three boards. Thestrings of the conventional piano are normally divided into threegroups. These may be classed as high notes, middle notes, and low notes.The sounding board of a piano is effectively divided into threesections. The smallest section is coupled to the highest notes and theremaining two sections become progressively larger as the lower notesare approached. By of notes, a somewhat smaller board to the middlesection coupling a large sounding board 142 to the lowest section of theelectronic piano, and a still smaller board to the highest notes, thepitch of the knock will be varied in the same manner which occurs in aconventional piano. This is illustrated in FIGURE 1 wherein a secondboard 142' is shown coupled to the middle section notes.

In the alternative, knock may be produced electronically. An electroniccircuit for so producing knock is shown in FIGURE 8. The coil 64 has oneterminal conneoted to the primary side of a coupling transformer 144.Its other terminal is connected to the opposite side of the transformerprimary through potentiometer resistance 146. The magnet 60 mounted onhammer 30 is illustrated schematically by means of an arrow. Thetransformer 144 couples the voltage pulse generated by the movablemagnet 60 to the base of transistor 148 through resistor 150. When thevoltage pulse generated in coil 64 is applied to the base of transistor148 it is caused to conducct, resulting in the charging of the capacitor152. The charge on capacitor 152 causes the transistors 154 and 156 toconduct and is doing so applies the voltage source E through a Hartleyoscillator and wave shaping circuit (not shown). The Hartley oscillatorand wave shaping circuit may be of a type similar to that shown inFIGURE 7. It should be apparent that the operation of the circuit shownin FIGURE 8 as thus far described is similar to that shown in FIGURE 7.

In order to generate a knock sound, the voltage pulse generated in coil64 is coupled through potentiometer 146 and matching transformer 158 toa tuned filter consisting of capacitors 210 and 212 and inductor 214.The tuned filter is tuned to a frequency approximating that of the knocksound. This frequency is connected to a preamplifier and amplifier whichamplify the sound and apply it to a transducing means such as aloudspeaker. In this manner, the knock sound may be electronicallyreproduced.

As has been previously described with respect to the circuit shown inFIGURE 7, the tone generating circuit may be provided with a circuit toselectively damp or sustain the generated signal. The damping circuit isillustrated by the resistor 90, diode 92 and switches 88 and 96. Thesecircuit elements operate in the same manner described with respect tothe circuit shown in FIGURE 7 and hence need not be further explained.

The creation of the psycho-acoustic effect wherein vibrations aretransferred back to the fingers of a player throughkeys 16 in anelectronic piano is accomplished as follows. A tuned cavity consistingof a box-like structure 218 is mounted on the bottom of the piano case.Tuned cavity 218 may be made of a long grain wood such as spruce and hasits open side mounted adjacent the bottom of the piano case. Thespeakers 86 are mounted in the bottom or closed side of cavity 218 sothat they broadcast into the cavity. Although four speakers are shown,it will be understood by those skilled in the art that the number ofspeakers may be varied in accordance with the size of the piano and typeof tone desired.

The tones broadcast into cavity 218 reflect off the bottom of the pianocase. As a result, a certain portion of their energy is transferred intothe Case and transmitted to the key frame 20 and keys 16 in much thesame manner that a conventional piano soundboard transmits sound energyto the piano keys.

The tuned cavity 218 also serves another purpose. That is, it serves toamplify the sound generated by speakers 86. The amount of soundamplification is a direct function of the size and shape of cavity 218.Thus, by varying the size and shape of cavity 218 it is possible to varythe overall sound of the piano. One distinct advantage of this is thatby using the same electronic equipment and speakers, and merely varyingthe size and shape of the tuned cavity 218, it is possible to select thecharacteristic sound of any one of a grand, baby grand, upright, orspinet type of piano. The construction of tuned cavities is known tothose skilled in the art and therefore it is not necessary to describethe modifications in cavity structure necessary to provide the above-setforth variations in tone or quality.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of thenvention.

We claim:

1. An electronic musical instrument including a key opera-ted action,velocity sensitive transducer means for directly transducing thevelocity of a struck key into an electric signal proportional thereto,said piano action including a movable core element associated therewith,said velocity sensitive transducer means including a coil, said coreelement being operative to vary the inductance of said coil inaccordance with the velocity of said key, audio output means forproducing an audio output in accordance with said transducer meanselectric signal, and knock producing means, said knock producing meansincluding a soundboard acoustically coupled to said transducer means forbroadcasting a sound energy pulse, said pulse being generated by themechanical shock energy of said piano action striking said transducermeans.

2. An electronic piano comprising a key operated piano action, velocitysensitive transducer means for directly transducing the velocity of astruck key into an electric signal proportional thereto, said pianoaction including a hammer, said hammer being controlled in its movementby said key and having a core element associated therewith, saidvelocity sensitive transducer means including a coil, said core elementbeing operative to vary the inductance of said coil in accordance withthe velocity of said hammer, audio output means for producing an audiooutput in accordance with said transducer means electric signal, andknock producing means, said knock producing means including a soundboardacoustically coupled to said transducer means for broadcasting a soundenergy pulse, said pulse being generated by the mechanical shock energyof said hammer striking said transducer means.

3. In an electronic musical instrument including a key operated action,velocity sensitive transducer means for directly transducing thevelocity of a struck key into an electric signal proportional thereto,said action includinga movable core element associated therewith, saidvelocity sensitive transducer means including a coil, said core elementbeing operative to vary the inductance of said coil in accordance withthe velocity of said key, audio output means for producing an audiooutput in accordance with said transducer means electric signal, andknock producing means, said knock producing means including a tunedcircuit coupled to said transducer means for modifying said electricsignal to have the frequency characteristics of a knock sound.

4. An electronic musical instrument comprising a plurality of keyoperated actions, each action having associated therewith a transducermeans for directly transducing the movement of a struck key into anelectric signal, each said action including a magnetic core, each saidtransducer means including a coil, said core being operative to vary theinductance of said coil in accordance with the movement of said key, anaudio output means for producing an audio output in accordance with saidtransducer means signal, said audio output means including a pluralityof tone generators, at least one tone generator coupled to eachtransducer means, each tone generator producing a characteristic tonesignal in response to said electric signal, said characteristic tonebeing representative of musical notes, and at least two knock producingmeans associated 'with distinct groupings of said transducer means, eachsaid knock producing means including a soundboard acoustically coupledto a grouping of said transducer means for broadcasting a sound energypulse, said pulse being generated by the mechanical shock energy of oneof said actions striking one of said transducer means.

5. An electronic musical instrument comprising a plurality of keyoperated actions, each action having associated therewith a magnetictransducer means for directly transducing the movement of a struck keyinto an electric signal, each said action including a magnetic coreelement, each said sensitive transducer means including a coil, saidcore element being operative to vary the inductance of said coil inaccordance with the movement of said key, an audio output means forproducing an audio output in accordance with said transducer means, saidaudio output means including a plurality of tone generators, at leastone tone generator coupled to each transducer means, each tone generatorproducing a characteristic signal in response to said electric signal,said characteristic signal being representative of musical tones, and atleast two knock producing means associated with distinct groupings ofsaid transducer means, said knock producing means including tunedcircuits coupled to said transducer means for modifying said electricsignal to have the frequency characteristics of a knock sound.

6. An electronic musical instrument comprising a plurality of keyoperated actions, each action having associated therewith a transducermeans for directly transducing the movement of a struck key into anelectric signal, each said action including a magnetic core element,each sensitive transducer means including a coil, said core elementbeing operative to vary the inductance of said coil in accordance withthe movement of said key, an audio output means for producing an audiooutput in accordance with said transducer means, said transducer coilsbeing positioned in close spatial relationship, and a metallic wrappingsurrounding said coils for limiting the extent of their magnetic fields,whereby the magnetic fields generated by said coils are not inductivelycoupled to adjacent coils.

7. An electronic musical instrument comprising a plurality of keyoperated actions, each action cooperating with a transducer means fordirectly transducing the movement of a struck key into an electricsignal, said action including a magnetic core element, each saidtransducer means including a coil, said magnetic core element beingoperative to vary the inductance of said coil in accordance with themovement of said key, an audio output means for producing an audiooutput in accordance with said transducer means signal, said magneticcore elements being positioned in close spatial relationship, a magneticshield adjacent said core elements, said magnetic shield being operativeto redirect the magnetic field of said magnetic core elements to preventtheir magnetic force fields from interacting.

8. An electronic musical instrument comprising a key operated action,velocity sensitive transducer means f l directly transducing thevelocity of a struck key into an electric signal proportional thereto,said action including a hammer, said hammer being controlled in itsmovement by said key and having a core element associated therewith,said velocity sensitive transducer means including a coil, a supportmounting said coil above said hammer and core element, at least aportion of said support being made of a transparent material, said coreelement being operative to vary the inductance of said coil inaccordance with the velocity of said key, an audio output means forproducing an audio output in accordance with said trans ducer meanselectric signal.

9. An electronic musical instrument comprising a key operated action, avelocity sensitive transducer means for directly transducing thevelocity of a struck key into an electric signal proportional thereto,said action including a core element connected therewith, said velocitysen sitive transducer means including a coil, said core element beingoperative to vary the inductance of said coil in accordance with thevelocity of said key, audio output means for producing an audio outputin accordance with said transducer means electric signal, said audiooutput means including means for transducing an electric tone signalinto an audio output, said last-mentioned means being coupled to a tunedcavity.

10. An electronic musical instrument comprising actuatable key means,transducer means for transducing the mechanical movement of a struck keyinto an electric signal, audio output means for producing an audiooutput in accordance with said transducer means electric signal, knockproducing means coupled to said transducer means for producing anaudible knock sound, said knock prw ducing means including a sound boardacoustically coupled to said instrument, and means for conducting tosaid 1 1 sound board an acoustic pulse generated by movement of anelement of said key means into contact with said instrument.

11. An electronic musical instrument comprising a key operated action,transducer means for directly transducing the mechanical movement of astruck key into an electric signal, an action including a movableelement connected therewith, said movable element cooperating with saidtransducer means to induce said electric signal, audio output means forproducing an audio output in accardance with the said transducer meanselectrical signal, means coupled to said transducer means for producingan audible knock sound, said knock producing means including a soundboard coupled to an acoustically conductive rod, said rod being coupledto said transducer means for conducting to said sound board anacoustical pulse generated by mechanical contact between said movableelement and said transducer means.

12. An electronic musical instrument comprising actuatable key means,transducer means for transducing the mechanical movement of a struck keyinto an electric signal, audio output means for producing an audiooutput in accordance with said transducer means electric signal, saidaudio output means including means for transducing an electric signalinto an audio ouput, and means for feeding audio sound vibrations backto the key means, said feed back means including a tuned cavity, saidtransducing means being coupled to said tuned cavity for radiating theaudio output into said tuned cavity, said tuned cavity beingmechanically fixed to a casing for said instrument, and said actuatablekey means being mechanically mounted to said casing.

13. An electronic musical instrument comprising a key operated action,transducer means for directly transducing the mechanical movement of astruck key into an electric signal, said action including a movableelement connected therewith, said movable element cooperating with saidtransducer means to induce said electric signal, audio output means forproducing an audio output in accordance with said transducer meanselectric signal, and means coupled to said transducer means forproducing a knock sound, said knock producing means including a tunedcircuit coupled to said transducer means for modifying said electricsignal to the frequency characteristics of a knock sound.

References Cited UNITED STATES PATENTS 2,619,866 12/1952 Bailey 843492,780,302 2/1957 George 181-31 2,952,179 9/1960 Andersen 841.243,248,470 4/1966 Markowitz et a1. 84-126 XR ARTHUR GAUSS, PrimaryExaminer.

JOHN ZAZWORSKY, Assistant Examiner.

US. Cl. X.R.

